Composition comprising silicone epoxy resin, hydroxyl compound, anhydride and curing catalyst

ABSTRACT

Epoxy resin compositions are disclosed which comprise (A) at least one silicone epoxy resin, (B) at least one hydroxyl-containing compound, (C) at least one anhydride curing agent, (D) at least one ancillary curing catalyst, and optionally at least one of thermal stabilizers, UV stabilizers, cure modifiers, coupling agents, or refractive index modifiers. Also disclosed are packaged solid state devices comprising a package, a chip ( 4 ), and an encapsulant ( 11 ) comprising an epoxy resin composition of the invention. A method of encapsulating a solid state device is also provided.

BACKGROUND OF THE INVENTION

This invention relates to epoxy resin compositions and solid statedevices encapsulated therewith. The invention also relates to a methodfor encapsulating a solid state device, such as a light emitting diode(LED).

Solid state devices, sometimes referred to as semiconductor devices oropto-electronic devices, comprise LEDs, CCDs, LSIs, photodiodes,phototransistors, photocouplers, opto-electronic couplers and the like.Such devices often exhibit special packaging needs. High-efficiency,high lumen, solid-state white LEDs require a novel packaging materialwhich can withstand more demanding conditions than those required bytypical low-intensity, longer wavelength LEDs. Common packagingmaterials will often undergo a gradual loss of optical and mechanicalproperties due to the combination of thermal, oxidative andphotodegradation processes.

Resins for encapsulation of solid state devices have primarily relied onblends of bisphenol-A epoxy resins and aliphatic anhydride curingagents. As described in U.S. Pat. No. 4,178,274, to Denk et al., onedisadvantage of these compositions, which harden fast through the use ofknown accelerators such as tertiary amines, imidazoles or borontrifluoride complexes, is their poor thermal aging stability. Thematerials used heretofore become discolored in extended storage attemperatures above 80° C. The resulting resins, which become yellow tobrown, have considerably reduced light transmittancy. Furthermore,because of the aromatic character of bisphenol-A based epoxy resins,these encapsulants are typically less stable to ultraviolet radiation.Therefore, these materials may tend to degrade on extended exposure tolight having an ultraviolet component. Such degradation can lead todiscoloration of the encapsulant and reduced light transmittance.

To circumvent these issues, Denk et al. describe resin compositions forthe sealing of opto-electronic components. These resins comprise a (i)cycloaliphatic epoxy resin, (ii) a carbonic acid anhydride (iii) zincoctoate and (iv) a solvent selected from the group consisting of a lowmolecular weight polyol, a low molecular weight ester and mixturesthereof. The compositions in Denk et al. are at most 46% epoxy resin byweight. Such low levels of epoxy resin and concomitant high levels ofcuring agents can lead to color formation in the cured resin, reducingthe overall transmittance of a LED.

Wada et al. in U.S. Pat. No. 5,145,889 describe a composition consistingessentially of (i) 100 parts by weight of an epoxy resin (ii) 70 to 140parts by weight of a curing agent including an acid anhydride (iii) 0.5to 4.0 parts by weight of a curing accelerator including an onium ordiazabicycloalkene salt (iv) 0.5 to 5.0 parts by weight of a phosphorustriphosphite and (v) 0.5 to 5.0 parts by weight of a silane couplingagent represented certain formulas. The compositions in Wada et al. areat most 58% epoxy resin by weight. Such high levels of curing agents canlead to color formation during thermal curing of the resin encapsulant,reducing the overall transmittance of a LED. Furthermore, saidencapsulating resin requires the use of a cure accelerator such as anonium or diazabicycloalkene salts to enhance cure rates and allow forreasonable processing times.

Ghoshal and Mukerji in U.S. Pat. No. 5,863,970 describe a compositionuseful as a die attach adhesive, polymer bump or encapsulating materialcomprising a mixture of silicone epoxy resin and non-silicone epoxyresins cured with an iodonium salt. The addition of non-silicone epoxyresin, especially an aromatic, bisphenol-A type epoxy resin, would makethe encapsulants less stable to ultraviolet radiation and temperatureexposure. Furthermore, materials such as diaryliodonium salts oftenproduce high colors upon cure.

There is a continuing need for novel packaging material for solid statedevices, such packaging material desirably possessing properties such ashigh transmission in a range from near UV to the visible wavelength;long term thermal, oxidative and UV stability; thermal compliance withother materials used to envelope the solid state device; low color; andhigh reflective index.

SUMMARY OF INVENTION

The present inventors have discovered curable resin compositions ideallysuited for an encapsulation of solid state devices such as lightemitting diodes. In one embodiment the present invention relates to acurable epoxy resin composition for encapsulation of a solid statedevice, which comprises (A) at least one silicone epoxy resin, (B) atleast one hydroxyl-containing compound, (C) at least one anhydridecuring agent, and (D) at least one ancillary curing catalyst.

In another embodiment of the present invention, there is provided apackaged solid state device comprising: (a) a package; (b) a chip; and(c) an encapsulant comprising: (A) at least one silicone epoxy resin,(B) at least one hydroxyl-containing compound, (C) at least oneanhydride curing agent, and (D) at least one ancillary curing catalyst.

In another embodiment of the present invention, there is provided amethod of encapsulating a solid state device comprising: placing a solidstate device into a package; and providing an encapsulant comprising:(A) at least one silicone epoxy resin, (B) at least onehydroxyl-containing compound, (C) at least one anhydride curing agent,and (D) at least one ancillary curing catalyst.

Various other features, aspects, and advantages of the present inventionwill become more apparent with reference to the following descriptionand appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a LED according to one embodimentof the present invention.

FIG. 2 is a schematic illustration of a LED according to anotherembodiment of the present invention.

FIG. 3 is a schematic illustration of a LED according to still anotherembodiment of the present invention.

DETAILED DESCRIPTION

Silicone epoxy resins useful as component (A) in the present inventioncomprise those known in the art. In some embodiments silicone epoxyresins comprise at least one silicon moiety selected from the groupconsisting of R₃SiO_(0.5) (M moieties), R₂SiO (D moieties), RSiO_(1.5)(T moieties), and SiO₂ (Q moieties), in combination with at least oneepoxy-containing silicone moiety selected from the group consisting ofEpR₂SiO_(0.5), EpRSiO, and EpSiO_(1.5), wherein Ep is an epoxy moietyselected from the group consisting of a glycidoxy propyl moiety as informula (I), a 3,4-epoxycyclohexane ethyl moiety as in formula (II), anda 1,2-epoxy hexyl moiety as in formula (III):

wherein R is monovalent alkyl, halogenated alkyl, or aryl, and R¹ ishydrogen or alkyl. In some embodiments R is selected from the groupconsisting of methyl, 3,3,3-trifluoropropyl, and phenyl, and mixturesthereof. In some embodiments R¹ is either hydrogen or methyl. Moietiesof the formulas (I), (II), and (III) are often derived fromhydrosilylation of an appropriate olefinic epoxy compound with Si—Hcontaining moiety. In particular embodiments silicone epoxy resinscomprise those depicted in formulas (IV), (V), (VI), (VII), (VIII), and(IX):

wherein the abbreviation “Ep” designates an epoxy-containing residuecomprising any of the epoxy structures depicted in formulas (I), (II),or (III); R is as previously defined; R² is monovalent alkyl,halogenated alkyl, or aryl; R³ is divalent alkyl, halogenated alkyl, oraryl; x is an integer between 1 and 4 inclusive; y is an integer between1 and 3 inclusive; z is an integer between 3 and 12 inclusive; and p isan integer having a value of 1 to about 80. In certain embodiments R instructures (IV)-(IX) is methyl. In a particular embodiment of structure(IV) R is methyl and Ep has the structure of formula (II) in which R¹ ishydrogen. In a particular embodiment of structure (IV) R is methyl andEp has the structure of formula (I). In a particular embodiment ofstructure (IV) R is methyl and Ep has the structure of formula (II) inwhich R¹ is methyl. In a particular embodiment of structure (IV) R ismethyl and Ep has the structure of formula (III). In certain embodimentsof structure (V) R is methyl and Ep has the structure of formula (II) inwhich R¹ is hydrogen. In a particular embodiment of structure (V) R ismethyl, x has the value of 4, and Ep has the structure of formula (II)in which R¹ is hydrogen. In certain embodiments of structure (VI) R ismethyl, R² is methyl or phenyl, and Ep has the structure of formula (II)in which R¹ is hydrogen. In a particular embodiment of structure (VI) Ris methyl, R² is methyl, y has the value of 3, and Ep has the structureof formula (II) in which R¹ is hydrogen. In a particular embodiment ofstructure (VI) R is methyl, R² is phenyl, y has the value of 3, and Ephas the structure of formula (II) in which R¹ is hydrogen. In aparticular embodiment of structure (VII) R is methyl, z has the value of4, and Ep has the structure of formula (II) in which R¹ is hydrogen. Incertain embodiments of structure (VIII) Ep has the structure of formula(II) in which R¹ is hydrogen, and p is an integer between about 1 andabout 70. In certain embodiments of structure (VIII) Ep has thestructure of formula (II) in which R¹ is hydrogen, and p is an integerbetween about 2 and about 70. In certain embodiments of structure (VIII)Ep has the structure of formula (II) in which R¹ is hydrogen, and p isan integer between about 50 and about 70. In certain embodiments ofstructure (VIII) Ep has the structure of formula (II) in which R¹ ishydrogen, and p is an integer between about 2 and about 5. In aparticular embodiment of structure (VIII) Ep has the structure offormula (II) in which R¹ is hydrogen, and p has the value of 2. Incertain embodiments of structure (IX) R³ is divalent alkyl and Ep hasthe structure of formula (II) in which R¹ is hydrogen. In certainembodiments of structure (IX) R³ is a straight-chain alkyl with 1 to 10carbon atoms and Ep has the structure of formula (II) in which R¹ ishydrogen. In certain embodiments of structure (IX) R³ is astraight-chain alkyl with 3 to 8 carbon atoms and Ep has the structureof formula (II) in which R¹ is hydrogen. In a particular embodiment ofstructure (IX) R³ is a straight-chain alkyl with 6 carbon atoms and Ephas the structure of formula (II) in which R¹ is hydrogen.

In other particular embodiments silicone epoxy resins comprise thosedepicted in formula (X):

wherein R and Ep are as previously defined; m is an integer betweenabout 20 and about 100; and n is an integer between about 1 and about20. In some embodiments of formula (X) R is methyl; Ep has the structureof formula (II) in which R¹ is hydrogen; m is an integer between about40 and about 100; and n is an integer between about 3 and about 10. Inother embodiments of formula (X) R is methyl; Ep has the structure offormula (II) in which R¹ is hydrogen; m is an integer between about 55and about 65; and n is an integer between about 3 and about 7.

Hydroxyl-containing additives useful as component (B) in the presentinvention comprise those with at least one OH group. In variousembodiments hydroxyl-containing additives comprise alcohols such aspolyfunctional alcohols such as diols, triols, etc., and bisphenols,trisphenols, etc. Further, the alcohol group in such compounds may beprimary, secondary or tertiary, or mixtures thereof. In particularembodiments the alcohol group is secondary or tertiary. Representativeexamples comprise benzyl alcohol, cyclohexanemethanol, alkyl diols,cyclohexanedimethanol, ethylene glycol, propylene glycol, butanediol,pentanediol, hexanediol, heptanediol, octanediol, polyethylene glycol,glycerol, polyether polyols such as those sold under the trade nameVORANOL by the Dow Chemical Company, and the like.

In some embodiments hydroxyl-containing additives useful as component(B) in the present invention comprise hydroxyl-containing siliconeresins. Hydroxyl-containing silicone resins comprise at least one Si—OHbond. In various embodiments silicone resins useful as component (B)comprise silicone T resins which contain at least one Si—OH bond. In aparticular embodiment silicone T resins useful as component (B) comprisethose with the formula (i): $\begin{matrix}{R_{a}^{4}S\quad i\quad {O_{(\frac{4 - a - b}{2})}\left( {O\quad H} \right)}_{b}} & (i)\end{matrix}$

wherein R⁴ is a monovalent hydrocarbon radical or a halogenatedmonovalent hydrocarbon radical. In various embodiments R⁴ is selectedfrom the group consisting of alkyl, methyl, ethyl, propyl, halogenatedalkyl, 3,3,3-trifluoropropyl, unsaturated alkyl, vinyl, aryl, phenyl,tolyl, benzyl, styryl, and mixtures thereof. In one embodiment siliconeT resin comprises a copolymer of the formula (i) in which R⁴ is amixture of methyl and phenyl groups. In another embodiment siliconeresins useful as component (B) comprise at least one silicone T/Dcopolymer. In a particular embodiment silicone resins useful ascomponent (B) comprise at least one silicone methyl/phenyl T/Dcopolymer. In various embodiments suitable silicone resins comprisestructural units of the formulas CH₃SiO_(3/2), (CH₃)₂SiO, (CH₃)₂SiO_(1/2), C₆H₅SiO_(3/2), (C₆H₅)₂SiO, (C₆H₅)(CH₃)SiO,(C₆H₅)(CH₃)SiO_(1/2), CH₂═CHSiO_(3/2), and mixtures thereof. Theparameter “a” has in one embodiment a value in a range of between about0.8 and about 1.9, in another embodiment a value in a range of betweenabout 1.0 and about 1.7, and in another embodiment a value in a range ofbetween about 1.1 and about 1.6. The parameter “b” has a value such thatin one embodiment at least about 0.2 wt. % OH groups are present in theresin, in another embodiment at least about 2 wt. % OH groups arepresent in the resin, and in another embodiment at least about 6 wt. %OH groups are present in the resin. In a particular embodiment suitablesilicone T resin comprises the hydrolysis product of a mixture ofphenyltrichlorosilane, methyltrichlorosilane, anddimethyldichlorosilane.

In some embodiments hydroxy-containing additives useful as component (B)may be substantially miscible with silicone epoxy resin employed ascomponent (A). Substantially miscible in the present context means thata mixture of hydroxyl-containing compound (component (B)) and siliconeepoxy resin (component (A)) exhibits single phase behavior and istransparent. In other embodiments hydroxy-containing additives useful ascomponent (B) may be at least partially miscible with silicone epoxyresin (A), or may be substantially immiscible with silicone epoxy resin(A). In some embodiments hydroxy-containing additives useful ascomponent (B) may be substantially miscible with silicone epoxy resinemployed as component (A), either at room temperature, or in a partiallycured state, or in a cured state. In other embodimentshydroxy-containing additives useful as component (B) may be at leastpartially miscible with silicone epoxy resin (A), either at roomtemperature, or in a partially cured state, or in a cured state. In oneembodiment a hydroxy-containing additive may be substantially immisciblewith silicone epoxy resin employed as component (A) at room temperature,and substantially miscible in a cured state.

Anhydride curing agents useful as component (C) in the present inventioncomprise those known in the art. Illustrative examples are described in“Chemistry and Technology of the Epoxy Resins” B. Ellis (Ed.) ChapmanHall, New York, 1993 and in “Epoxy Resins Chemistry and Technology”,edited by C. A. May, Marcel Dekker, New York, 2nd edition, 1988. Invarious embodiments anhydride curing agents comprise at least one ofbicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic anhydride,methylbicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic anhydride,bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic anhydride, phthalic anhydride,pyromellitic dianhydride, hexahydrophthalic anhydride,hexahydro-4-methylphthalic anhydride, dodecenylsuccinic anhydride,dichloromaleic anhydride, chlorendic anhydride, tetrachlorophthalicanhydride, and the like. Mixtures comprising at least two anhydridecuring agents may also be used.

The amounts of silicone epoxy resin (A), hydroxyl-containing compound(B), and curing agent (C) can be varied over a wide range. In variousembodiments the amount of silicone epoxy resin (A) in the composition isgreater than about 40% by weight based on the combined weight ofsilicone epoxy resin (A), hydroxyl-containing compound (B), curing agent(C), and ancillary curing catalyst (D). In some embodiments the amountof silicone epoxy resin (A) in the composition is in a range of betweenabout 40% by weight and about 99% by weight based on the combined weightof silicone epoxy resin (A), hydroxyl-containing compound (B), curingagent (C), and ancillary curing catalyst (D). In other embodiments theamount of silicone epoxy resin (A) in the composition is in a range ofbetween about 76% by weight and about 99% by weight based on thecombined weight of silicone epoxy resin (A), hydroxyl-containingcompound (B), curing agent (C), and ancillary curing catalyst (D).

In various embodiments the amount of hydroxyl-containing compound (B)inthe composition is in a range of between about 1% by weight and about20% by weight based on the combined weight of silicone epoxy resin (A),hydroxyl-containing compound (B), curing agent (C), and ancillary curingcatalyst (D). In other embodiments the amount of hydroxyl-containingcompound (B) in the composition is in a range of between about 2% byweight and about 10% by weight based on the combined weight of siliconeepoxy resin (A), hydroxyl-containing compound (B), curing agent (C), andancillary curing catalyst (D). In some embodiments the amount ofhydroxyl-containing compound (B) in the composition is in a range ofbetween about 4% by weight and about 8% by weight based on the combinedweight of silicone epoxy resin (A), hydroxyl-containing compound (B),curing agent (C), and ancillary curing catalyst (D).

In various embodiments the amount of curing agent (C) in the compositionis less than about 40% by weight based on the combined weight ofsilicone epoxy resin (A), hydroxyl-containing compound (B), curing agent(C), and ancillary curing catalyst (D). In other embodiments the amountof curing agent (C) in the composition is less than about 25% by weightbased on the combined weight of silicone epoxy resin (A),hydroxyl-containing compound (B), curing agent (C), and ancillary curingcatalyst (D). In some embodiments the amount of curing agent (C) in thecomposition is in a range of between about 1% by weight and about 24% byweight based on the combined weight of silicone epoxy resin (A),hydroxyl-containing compound (B), curing agent (C), and ancillary curingcatalyst (D). In other embodiments the amount of curing agent (C) in thecomposition is in a range of between about 10% by weight and about 20%by weight based on the combined weight of silicone epoxy resin (A),hydroxyl-containing compound (B), curing agent (C), and ancillary curingcatalyst (D).

Ancillary curing catalysts useful as component (D) in the presentinvention comprise those known in the art. Illustrative examples aredescribed in “Chemistry and Technology of the Epoxy Resins” edited by B.Ellis, Chapman Hall, New York, 1993, and in “Epoxy Resins Chemistry andTechnology”, edited by C. A. May, Marcel Dekker, New York, 2nd edition,1988. In various embodiments the ancillary curing catalyst comprises anorganometallic salt, a sulfonium salt or an iodonium salt. In particularembodiments the ancillary curing catalyst comprises at least one of ametal carboxylate, a metal acetylacetonate, zinc octoate, stannousoctoate, triarylsulfonium hexafluorophosphate, triarylsulfoniumhexafluoroantimonate (such as CD 1010 sold by Sartomer Corporation),diaryliodonium hexafluoroantimonate, or diaryliodoniumtetrakis(pentafluorophenyl)borate. In various embodiments the amount ofancillary curing catalyst (D) in the composition is less than about 10%by weight based on the combined weight of silicone epoxy resin (A),hydroxyl-containing compound (B), curing agent (C), and ancillary curingcatalyst (D). In some embodiments the amount of ancillary curingcatalyst (D) in the composition is in a range between about 0.008% byweight and about 10% by weight based on the combined weight of siliconeepoxy resin (A), hydroxyl-containing compound (B), curing agent (C), andancillary curing catalyst (D). In other embodiments the amount ofancillary curing catalyst (D) in the composition is in a range betweenabout 0.01% by weight and about 5% by weight based on the combinedweight of silicone epoxy resin (A), hydroxyl-containing compound (B),curing agent (C), and ancillary curing catalyst (D). In some embodimentsthe amount of ancillary curing catalyst (D) in the composition is in arange between about 0.01% by weight and about 1.0% by weight based onthe combined weight of silicone epoxy resin (A), hydroxyl-containingcompound (B), curing agent (C), and ancillary curing catalyst (D). Inother embodiments the amount of ancillary curing catalyst (D) in thecomposition is in a range between about 0.01% by weight and about 0.5%by weight based on the combined weight of silicone epoxy resin (A),hydroxyl-containing compound (B), curing agent (C), and ancillary curingcatalyst (D).

One or more thermal stabilizers or UV-stabilizers or mixtures thereofmay optionally be present in the compositions of the invention. Suchstabilizers may reduce color formation during processing of theencapsulant. Many stabilizers to improve the thermal and or UV stabilityare known in the art and have been described in numerous patents andpublications such as in J. F. Rabek, “Photostabilization of Polymers;Principles and Applications”, Elsevier Applied Science, NY, 1990 and in“Plastics Additives Handbook”, 5th edition, edited by H. Zweifel, HanserPublishers, 2001. Illustrative examples of suitable stabilizers compriseorganic phosphites and phosphonites, such as triphenyl phosphite,diphenylalkyl phosphites, phenyldialkyl phosphites, tri-(nonylphenyl)phosphite, trilauryl phosphite, trioctadecyl phosphite,di-stearyl-pentaerythritol diphosphite, tris-(2,4-di-tert-butylphenyl)phosphite, di-isodecylpentaerythritol diphosphite,di-(2,4-di-tert-butylphenyl) pentaerythritol diphosphite,tristearyl-sorbitol triphosphite, andtetrakis-(2,4-di-tert-butylphenyl)-4,4′-biphenyldiphosphonite.Illustrative examples of suitable stabilizers also comprisesulfur-containing phosphorus compounds such as trismethylthiophosphite,trisethylthiophosphite, trispropylthiophosphite,trispentylthiophosphite, trishexylthiophosphite,trisheptylthiophosphite, trisoctylthiophosphite, trisnonylthiophosphite,trislaurylthiophosphite, trisphenylthiophosphite,trisbenzylthiophosphite, bispropiothiomethylphosphite,bispropiothiononylphosphite, bisnonylthiomethylphosphite,bisnonylthiobutylphosphite, methylethylthiobutylphosphite,methylethylthiopropiophosphite, methylnonylthiobutylphosphite,methylnonylthiolaurylphosphite, and pentylnonylthiolaurylphosphite.These compounds can be used singly or in a combination of at least twocompounds.

Suitable stabilizers also comprise sterically hindered phenols which areknown in the art. Illustrative examples of sterically hindered phenolstabilizers comprise 2-tertiary-alkyl-substituted phenol derivatives,2-tertiary-amyl-substituted phenol derivatives,2-tertiary-octyl-substituted phenol derivatives,2-tertiary-butyl-substituted phenol derivatives,2,6-di-tertiary-butyl-substituted phenol derivatives,2-tertiary-butyl-6-methyl- (or 6-methylene-) substituted phenolderivatives, and 2,6-di-methyl-substituted phenol derivatives. Thesecompounds can be used singly or in a combination of at least twocompounds. In certain particular embodiments sterically hindered phenolstabilizers comprise alpha-tocopherol and butylated hydroxy toluene.

Suitable stabilizers also comprise sterically hindered amines,illustrative examples of which comprisebis-(2,2,6,6-tetramethylpiperidyl) sebacate,bis-(1,2,2,6,6-pentamethylpiperidyl) sebacate,n-butyl-3,5-di-tert-butyl-4-hydroxybenzyl malonic acidbis-(1,2,2,6,6-pentamethylpiperidyl)ester, condensation product of1-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinicacid, condensation product ofN,N′-(2,2,6,6-tetramethylpiperidyl)-hexamethylenediamine and4-tert-octyl-amino-2,6-dichloro-s-triazine,tris-(2,2,6,6-tetramethylpiperidyl)-nitrilotriacetate,tetrakis-(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate,and 1,1′-(1,2-ethanediyl)-bis-(3,3,5,5-tetramethylpiperazinone). Thesecompounds can be used singly or in a combination of at least twocompounds.

Suitable stabilizers also comprise compounds which destroy peroxide,illustrative examples of which comprise esters of beta-thiodipropionicacid, for example the lauryl, stearyl, myristyl or tridecyl esters;mercaptobenzimidazole or the zinc salt of 2-mercaptobenzimidazole; zincdibutyl-dithiocarbamate; dioctadecyl disulfide; and pentaerythritoltetrakis-(beta-dodecylmercapto)-propionate. These compounds can be usedsingly or in a combination of at least two compounds.

Optional components in the present invention also comprise curemodifiers which may modify the rate of cure of epoxy resin. In variousembodiments cure modifiers comprise at least one of cure accelerators orcure inhibitors. Cure modifiers may comprise compounds containingheteroatoms that possess lone electron pairs. Phosphites may be used ascure modifiers. Illustrative examples of phosphites comprisetrialkylphosphites, triarylphosphites, trialkylthiophosphites, andtriarylthiophosphites. In some embodiments phosphites comprise triphenylphosphite, benzyldiethyl phosphite, or tributyl phosphite. Othersuitable cure modifiers comprise sterically hindered amines and2,2,6,6-tetramethylpiperidyl residues, such as for examplebis(2,2,6,6-tetramethylpiperidyl) sebacate. Mixtures of cure modifiersmay also be employed.

Optional components in the present invention also comprise couplingagents which in various embodiments may help epoxy resin bind to amatrix, such as a glass matrix, so as to form a strong bond to thesurface such that premature failure does not occur. Coupling agentscomprise compounds that contain both silane and mercapto moieties,illustrative examples of which comprise mercaptomethyltriphenylsilane,beta-mercaptoethyltriphenylsilane, beta-mercaptopropyltriphenylsilane,gamma-mercaptopropyldiphenylmethylsilane,gamma-mercaptopropylphenyldimethylsilane,delta-mercaptobutylphenyldimethylsilane,delta-mercaptobutyltriphenylsilane, tris(beta-mercaptoethyl)phenylsilane, tris(gamma-mercaptopropyl)phenylsilane,tris(gamma-mercaptopropyl)methylsilane,tris(gamma-mercaptopropyl)ethylsilane, andtris(gamma-mercaptopropyl)benzylsilane. Coupling agents also comprisecompounds which comprise both an alkoxysilane and an organic moiety,illustrative examples of which comprise compounds of the formula(R⁵O)₃Si—R⁶ wherein R⁵ is an alkyl group and R⁶ is selected from thegroup consisting of vinyl, 3-glycidoxypropyl, 3-mercaptopropyl,3-acryloxypropyl, 3-methacryloxypropyl, and C_(n)H_(2n+1). In someembodiments R⁵ is methyl or ethyl, and n has the value of 4-16. In otherembodiments coupling agents comprise those comprising both analkoxysilane and an epoxy moiety. Coupling agents can be used singly orin a combination of at least two compounds.

Optional components in the present invention also comprise refractiveindex modifiers. As light passes from the relatively high index ofdiffraction chip (typically 2.8-3.2) to the lower refractive index epoxyencapsulant (typically 1.2-1.6) some of the light is reflected back tothe chip at the critical angle. Modifiers with high refractive indexadded to the epoxy increase its refractive index, producing a bettermatch of the two refractive indices and an increase in the amount ofemitted light. Such materials increase the refractive index of the epoxywithout significantly affecting the transparency of the epoxyencapsulant. Modifiers of this type comprise additives with highrefractive index. These materials comprise optically transparentorganics or inorganics, and agglomerates of particles or structureswhose size is less than the size of the wavelength of the emitted light.Such agglomerates are sometimes referred to as nanoparticles. Suchmaterials are known in the art and comprise a variety of transparentmetal oxides or group II-VI materials that are relatively free fromscattering. In one embodiment, a nanoparticle material is titaniumdioxide. In other embodiments other types of transparent metal oxides orcombinations of metal oxides can be used. For example, magnesium oxide,yttria, zirconia, cerium oxides, alumina, lead oxides, and compositematerials such as those comprising yttria and zirconia can be used toproduce nanoparticles. In yet other embodiments nanoparticles are madefrom one of the group II-VI materials comprising zinc selenide, zincsulphide, and alloys made from Zn, Se, S, and Te. Alternatively, galliumnitride, silicon nitride, or aluminum nitride can be also used to makenanoparticles.

The compositions of the present invention can be prepared by combiningthe various components, including optional components, in any convenientorder. In various embodiments all the components may be mixed together.In other embodiments two or more components may be premixed and thensubsequently combined with other components. In one embodiment thecomponents of the compositions of the invention comprise a two-partcomposition, wherein the various components are premixed in at least twoseparate compositions before combination to provide a final composition.

Encapsulation techniques for solid state devices are well known to theart and may be used in the present invention. In various embodimentssuch techniques comprise casting, resin transfer molding and the like.After the solid state device is enveloped in the uncured resin,typically performed in a mold, the resin is cured. These resins may becured in one or more stages using art-known methods comprising thermal,UV or electron beam techniques or combination thereof. For example,thermal cure may be performed at temperatures in one embodiment in arange of from about room temperature to about 200° C., in anotherembodiment in a range of from about 80° C. to about 200° C., in anotherembodiment in a range of from about 100° C. to about 200° C., and inanother embodiment in a range of from about 120° C. to about 160° C.Also in other embodiments these materials can be photo-chemically cured,initially at about room temperature, using art-known techniques.Although some thermal excursion from the photochemical reaction andsubsequent cure can occur, no external heating is typically required. Inother embodiments these materials may be cured in two stages wherein aninitial thermal or UV cure, for example, may be used to produce apartially hardened or B-staged epoxy resin. This material, which iseasily handled, may then be further cured using, for example, eitherthermal or UV techniques, to produce a material with the desired thermalperformance (for example Tg, CTE), optical properties and moistureresistance required for encapsulated solid state devices.

Without further elaboration, it is believed that one skilled in the artcan, using the description herein, utilize the present invention to itsfullest extent. The following examples are included to provideadditional guidance to those skilled in the art in practicing theclaimed invention. The examples provided are merely representative ofthe work that contributes to the teaching of the present application.Accordingly, these examples are not intended to limit the invention, asdefined in the appended claims, in any manner.

EXAMPLES 1-3

Epoxy resin encapsulants were prepared by combining the variousepoxy-comprising resins, curing agents and other components as shown inTable 1, and curing under the specified conditions. All quantities arein parts by weight. The abbreviation “RT” means room temperature. Thecomposition of Example 3 also contained 0.08 wt. % of a hindered phenolstabilizer and 0.08 wt. % of a phosphite stabilizer.1,1,3,3-Tetramethyl-1,3-bis[2(7-oxabicyclo[4.1.0]hept-3-yl)ethyl]disiloxanewas employed as silicone epoxy resin. The hydroxyl-containing compound(B) was a hydroxyl-containing silicone resin comprising the hydrolysisproduct of a mixture of phenyltrichlorosilane, methyltrichlorosilane,and dimethyldichlorosilane.

TABLE 1 Component Ex. 1 Ex. 2 Ex. 3 Component A epoxy resin3,4-epoxycyclohexylmethyl-3,4- 73 28.9 — epoxycyclohexanecarboxylate(ERL 4221D) bisphenol-A diglycidyl ether oligomer — 36.2 — (EPON 828)silicone epoxy resin — — 78.38 Component B hydroxyl-containing siliconecompound — — 5.42 2,5-hexanediol 3 — — Component C curing agenthexahydro-4-methylphthalic anhydride 17 32.2 15.58 Component D ancillarycuring catalyst trimethoxyboroxine 3 — — zinc octoate — 0.1 0.46Optional components triphenyl phosphite 2 2.6 —glycidoxypropyltrimethoxysilane 2 — — Processing Cure time, time(hrs.)/temp. (° C.) 1/110, 4/150 0.5/120, then then 3/150 3.5/150Properties Tg (° C.) 131 127 141 Pot life (min.)* 4 12 12 *values areapproximate

The values for initial % transmission at a wavelength were measured on 5mm thick specimens. The values are shown in Table 2.

TABLE 2 % transmission at wavelength Ex. 1 Ex. 2 Ex. 3 360 49.40 27.3653.70 370 60.62 42.35 63.44 380 69.57 57.13 71.77 390 75.57 66.89 78.35400 79.72 73.40 83.29 410 82.48 77.29 86.50 420 84.35 79.70 88.40 43085.67 82.02 89.58 440 86.69 83.70 90.33 450 87.39 84.85 90.81 460 87.9685.72 91.16 470 88.44 86.49 91.42 480 88.76 87.08 91.59 490 89.04 87.4991.73 500 89.24 87.79 91.81 510 89.40 88.04 91.88 520 89.57 88.26 91.93530 89.68 88.40 91.98 540 89.76 88.51 92.01 550 89.87 88.61 92.03 56089.93 88.71 92.05 570 89.96 88.77 92.07 580 90.00 88.79 92.07 590 90.0388.83 92.09 600 90.08 88.90 92.10 610 90.06 88.89 92.08 620 90.06 88.9192.11 630 90.09 88.94 92.10 640 90.11 88.99 92.11 650 90.15 89.02 92.15660 90.16 89.02 92.18 670 90.17 89.02 92.18 680 90.18 89.05 92.15 69090.21 89.07 92.24 700 90.23 89.09 92.24 710 90.25 89.10 92.19 720 90.2389.09 92.24 730 90.21 89.11 92.18 740 90.07 89.02 92.02 750 89.92 88.9091.79

A composition of the invention (Example 3) shows improved initialtransmission especially in the near UV region of the spectrum (about400-450 nm) compared to Example 1 containing cycloaliphatic epoxy resinand Example 2 containing aromatic epoxy resin.

The values for % transmission at a wavelength were also measured on 5 mmthick specimens after 500 hours exposure in a Weatherometer using axenon lamp with filter to cut off radiation below wavelength of 380 nm.The values are shown in Table 3.

TABLE 3 % transmission at wavelength Ex. 1 Ex. 2 Ex. 3 360 68.16 53.1671.00 370 74.79 64.40 77.21 380 78.98 71.98 81.33 390 81.63 76.77 84.16400 83.38 79.85 86.10 410 84.52 81.71 87.68 420 85.36 83.05 88.67 43085.97 84.06 89.36 440 86.51 84.92 89.89 450 86.97 85.63 90.28 460 87.3686.21 90.57 470 87.77 86.75 90.81 480 87.96 87.15 90.97 490 88.19 87.5291.10 500 88.36 87.81 91.21 510 88.47 88.06 91.28 520 88.60 88.27 91.36530 88.72 88.47 91.42 540 88.79 88.58 91.46 550 88.88 88.74 91.49 56088.93 88.84 91.50 570 88.98 88.94 91.51 580 89.01 89.01 91.53 590 89.0689.09 91.53 600 89.12 89.13 91.55 610 89.11 89.18 91.55 620 89.17 89.2391.55 630 89.22 89.26 91.55 640 89.29 89.30 91.59 650 89.37 89.35 91.63660 89.43 89.39 91.66 670 89.45 89.41 91.68 680 89.51 89.45 91.71 69089.61 89.53 91.79 700 89.62 89.51 91.79 710 89.62 89.51 91.78 720 89.6789.56 91.82 730 89.60 89.54 91.74 740 89.50 89.46 91.60 750 89.33 89.2891.39

A composition of the invention (Example 3) shows improved UV stabilityand improved transmission especially in the near UV region of thespectrum (about 400-450 nm) compared to Example 1 containingcycloaliphatic epoxy resin and Example 2 containing aromatic epoxyresin.

The values for % transmission at a wavelength were measured on 5 mmthick specimens after 500 hours exposure to a temperature of 150° C. Thevalues are shown in Table 4.

TABLE 4 % transmission at wavelength Ex. 1 Ex. 2 Ex. 3 360 17.86 6.7434.98 370 28.21 13.94 44.48 380 39.09 25.34 54.07 390 48.73 36.46 62.90400 57.14 46.32 70.32 410 64.26 54.43 75.90 420 69.85 60.88 79.77 43074.21 66.28 82.55 440 77.51 70.60 84.53 450 80.10 74.10 85.93 460 82.1576.96 86.99 470 83.78 79.33 87.86 480 85.01 81.25 88.53 490 86.01 82.8489.08 500 86.76 84.08 89.53 510 87.37 85.06 89.90 520 87.81 85.80 90.21530 88.22 86.42 90.53 540 88.52 86.94 90.79 550 88.75 87.32 91.03 56088.96 87.63 91.25 570 89.10 87.87 91.41 580 89.23 88.06 91.53 590 89.3488.21 91.68 600 89.42 88.37 91.82 610 89.46 88.44 91.90 620 89.51 88.5491.94 630 89.53 88.62 92.00 640 89.57 88.68 92.04 650 89.61 88.75 92.10660 89.64 88.77 92.15 670 89.64 88.78 92.17 680 89.68 88.83 92.21 69089.70 88.89 92.25 700 89.70 88.85 92.24 710 89.70 88.85 92.26 720 89.7188.90 92.27 730 89.64 88.85 92.22 740 89.52 88.76 92.03 750 89.33 88.5991.87

A composition of the invention (Example 3) shows improved thermalstability and improved transmission especially in the near UV region ofthe spectrum (about 400-450 nm) compared to Example 1 containingcycloaliphatic epoxy resin and Example 2 containing aromatic epoxyresin.

The epoxy resin compositions of the present invention can be used inapplications known for epoxy resin compositions. Such applicationscomprise coatings, potting compounds, and encapsulants for solid statedevices. In one embodiment a solid state device is a LED. FIG. 1schematically illustrates a LED 1 according to one embodiment of thepresent invention. The LED 1 contains a LED chip 4, which iselectrically connected to a lead frame 5. For example, the LED chip 4may be directly electrically connected to an anode or cathode electrodeof the lead frame 5 and connected by a lead 7 to the opposite cathode oranode electrode of the lead frame 5, as illustrated in FIG. 1. In aparticular embodiment illustrated in FIG. 1, the lead frame 5 supportsthe LED chip 4. However, the lead 7 may be omitted, and the LED chip 4may straddle both electrodes of the lead frame 5 with the bottom of theLED chip 4 containing the contact layers, which contact both the anodeand cathode electrode of the lead frame 5. Alternatively, the LED chip 4may be connected with a separate lead 7 to the cathode and the anodeelectrode of the lead frame 5. The lead frame 5 connects to a powersupply, such as a current or voltage source or to another circuit (notshown).

The LED chip 4 emits radiation from the radiation emitting surface 9.The LED may emit visible, ultraviolet or infrared radiation. The LEDchip may comprise any LED chip containing a p-n junction of anysemiconductor layers capable of emitting the desired radiation. Forexample, the LED chip may contain any desired Group III-V compoundsemiconductor layers, such as GaAs, GaAlAs, GaN, InGaN, GaP, etc., orGroup II-VI compound semiconductor layers such ZnSe, ZnSSe, CdTe, etc.,or Group IV-IV semiconductor layers, such as SiC. The LED chip 4 mayalso contain other layers, such as cladding layers, waveguide layers andcontact layers.

The LED 1 is packaged with an encapsulant 11 of the present invention.An alternative term for encapsulant is encapsulating material. In oneembodiment the LED packaging includes encapsulant 11 located in apackage, such as a shell 14. The shell may be any plastic or othermaterial, such as polycarbonate, which is transparent to the LEDradiation. However, the shell 14 may be omitted to simplify processingif encapsulant 11 has sufficient toughness and rigidity to be usedwithout a shell. Thus, the outer surface of encapsulant 11 would act insome embodiments as a shell 14 or package. The shell 14 contains a lightor radiation emitting surface 15 above the LED chip 4 and a non-emittingsurface 16 adjacent to the lead frame 5. The radiation emitting surface15 may be curved to act as a lens and/or may be colored to act as afilter. In various embodiments the non-emitting surface 16 may be opaqueto the LED radiation, and may be made of opaque materials such as metal.The shell 14 may also contain a reflector around the LED chip 4, orother components, such as resistors, etc., if desired.

In other embodiments encapsulating materials may optionally contain aphosphor to optimize the color output of the LED 1. For example, aphosphor may be interspersed or mixed as a phosphor powder withencapsulant 11 or coated as a thin film on the LED chip 4 or coated onthe inner surface of the shell 14. Any phosphor material may be usedwith the LED chip. For example, a yellow emitting cerium doped yttriumaluminum garnet phosphor (YAG:Ce³⁺) may be used with a blue emittingInGaN active layer LED chip to produce a visible yellow and blue lightoutput which appears white to a human observer. Other combinations ofLED chips and phosphors may be used as desired.

While the packaged LED chip 4 according to one embodiment illustrated inFIG. 1 is supported by the lead frame 5, the LED 1 can have variousother structures. For example, the LED chip 4 may be supported by thebottom surface 16 of the shell 14 or by a pedestal (not shown) locatedon the bottom of the shell 14, instead of by the lead frame 5.

In another embodiment of the present invention, the LED chip 4 of theLED 2 may be supported by a carrier substrate 17, as illustrated in FIG.2. The carrier substrate 17 comprises a lower portion of the LEDpackage, and may comprise any material, such as plastic, metal orceramic. Preferably, the carrier substrate is made out of plastic andcontains a groove 19 in which the LED chip 4 is located. The sides ofthe groove 19 may be coated with a reflective metal 21, such asaluminum, which acts as a reflector. However, the LED chip 4 may beformed over a flat surface of the substrate 17. The substrate 17contains electrodes 23 that electrically contact the contact layers ofthe LED chip 4. Alternatively, the electrodes 23 may be electricallyconnected to the LED chip 4 with one or two leads as illustrated in FIG.1. If desired, the shell 14 or a glass plate may be formed over theencapsulant 11 to act as a lens or protective material.

In another embodiment of the present invention a LED array 3 may befabricated on a plastic substrate, as illustrated in FIG. 3. The LEDchips or die 4 are physically and electrically mounted on cathode leads26. The top surfaces of the LED chips 4 are electrically connected toanode leads 25 with lead wires 27. The lead wires may be attached byknown wire bonding techniques to a conductive chip pad. The leads 26, 25comprise a lead frame and may be made of a metal, such as silver platedcopper. The lead frame and LED chip array 3 are contained in a plasticpackage 29, such as a polycarbonate package. In some embodiments thepolycarbonate comprises a bisphenol A polycarbonate. The plastic package29 is filled with an encapsulant 11 of the present invention. Thepackage 29 contains tapered interior sidewalls 18, which enclose the LEDchips 4, and form a light spreading cavity 20, which ensures crossfluxing of LED light.

While the invention has been illustrated and described in typicalembodiments, it is not intended to be limited to the details shown,since various modifications and substitutions can be made withoutdeparting in any way from the spirit of the present invention. As such,further modifications and equivalents of the invention herein disclosedmay occur to persons skilled in the art using no more than routineexperimentation, and all such modifications and equivalents are believedto be within the spirit and scope of the invention as defined by thefollowing claims. All Patents cited herein are incorporated herein byreference.

What is claimed is:
 1. A curable epoxy resin composition forencapsulation of a solid state device, which comprises (A) at least onesilicone epoxy resin, (B) at least one hydroxyl-containing compound. (C)at least one anhydride curing agent, and (D) at least one ancillarycuring catalyst, wherein component (A) is present at a level of greaterthan about 40% by weight; component (B) is present at a level in a rangeof between about 1% by weight and about 20% by weight; component (C) ispresent at a level of less than about 25% by weight; and component (D)is present at a level in a range between about 0.008% by weight andabout 10% by weight based on the combined weight of silicone epoxy resin(A), hydroxyl-containing compound (B), curing agent (C), and ancillarycuring catalyst (D).
 2. The composition of claim 1, wherein the siliconeepoxy resin (A) comprises at least one silicon moiety selected from thegroup consisting of R₃SiO_(0.5), R₂SiO, RSiO_(1.5), and SiO₂, incombination with at least one epoxy-containing silicone moiety selectedfrom the group consisting of EpR₂SiO_(0.5), EpRSiO, and EpSiO_(1.5),wherein Ep is an epoxy moiety selected from the group consisting of aglycidoxy propyl moiety as in formula (I), a 3,4-epoxycyclohexane ethylmoiety as in formula (II), and a 1,2-epoxy hexyl moiety as in formula(III):

wherein R is monovalent alkyl, halogenated alkyl, or aryl, and R¹ ishydrogen or alkyl.
 3. The composition of claim 2, wherein the siliconeepoxy resin (A) comprises at least one compound selected from the groupconsisting of those depicted in formulas (IV), (V), (VI), (VII), (VIII),(IX), and (X):

wherein the abbreviation “Ep” designates any of the epoxy structuresdepicted in formulas (I), (II), or (III); R and R² are eachindependently monovalent alkyl, halogenated alkyl, or aryl; R³ isdivalent alkyl, halogenated alkyl, or aryl; x is an integer between 1and 4 inclusive; y is an integer between 1 and 3 inclusive; z is aninteger between 3 and 12 inclusive; p is an integer having a value of 1to about 80; m is an integer between about 20 and about 100; and n is aninteger between about 1 and about
 20. 4. The composition of claim 3,wherein the silicone epoxy resin (A) comprises1,1,3,3-tetramethyl-1,3-bis[2(7-oxabicyclo[4.1.0]hept-3-yl)ethyl]disiloxane.5. The composition of claim 1, wherein the hydroxyl-containing compound(B) comprises at least one compound selected from the group consistingof a primary alcohol, a secondary alcohol, a tertiary alcohol, apolyfunctional alcohol, a diol, a triol, a bisphenol, a trisphenol,benzyl alcohol, cyclohexanemethanol, an alkyl diol,cyclohexanedimethanol, ethylene glycol, propylene glycol, butanediol,pentanediol, hexanediol, heptanediol, octanediol, polyethylene glycol,glycerol, a polyether polyol, at least one compound with the formula(i): $\begin{matrix}{R_{a}^{4}S\quad i\quad {O_{(\frac{4 - a - b}{2})}\left( {O\quad H} \right)}_{b}} & (i)\end{matrix}$

wherein R⁴ is a monovalent hydrocarbon radical or a halogenatedmonovalent hydrocarbon radical; and mixtures thereof.
 6. The compositionof claim 5, wherein the value for the parameter b is such that at leastabout 0.2 wt. % OH groups are present in hydroxyl-containing compound(B).
 7. The composition of claim 5, wherein the hydroxyl-containingcompound (B) comprises at least one silicone T resin.
 8. The compositionof claim 5, wherein the hydroxyl-containing compound (B) comprises atleast one silicone T/D copolymer.
 9. The composition of claim 8, whereinR⁴ comprises a mixture of methyl and phenyl groups.
 10. The compositionof claim 9, wherein hydroxyl-containing compound (B) comprises thehydrolysis product of a mixture of phenyltrichlorosilane,methyltrichlorosilane, and dimethyldichlorosilane.
 11. The compositionof claim 1, wherein the anhydride curing agent (C) comprises at leastone member selected from the group consisting ofbicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic anhydride,methylbicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic anhydride,bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic anhydride, phthalic anhydride,pyromellitic dianhydride, hexahydrophthalic anhydride,hexahydro-4-methylphthalic anhydride, dodecenylsuccinic anhydride,dichloromaleic anhydride, chlorendic anhydride, and tetrachlorophthalicanhydride.
 12. The composition of claim 11, wherein the anhydride curingagent (C) comprises hexahydro-4-methylphthalic anhydride.
 13. Thecomposition of claim 1, wherein the ancillary curing catalyst (D)comprises at least one member selected from the group consisting of anorganometallic salt, a sulfonium salt and an iodonium salt.
 14. Thecomposition of claim 13, wherein the ancillary curing catalyst (D)comprises at least one member selected from the group consisting of ametal carboxylate, a metal acetylacetonate, zinc octoate, stannousoctoate, triarylsulfonium hexafluorophosphate, triarylsulfoniumhexafluoroantimonate, diaryliodonium hexafluoroantimonate, anddiaryliodonium tetrakis(pentafluorophenyl)borate.
 15. The composition ofclaim 1, further comprising at least one of thermal stabilizers, UVstabilizers, cure modifiers, coupling agents, or refractive indexmodifiers.
 16. The composition of claim 15, comprising at least one of athermal stabilizer or a UV stabilizer.
 17. The composition of claim 16,comprising at least one of a hindered phenol stabilizer or a phosphitestabilizer.
 18. The partially cured composition of claim
 1. 19. Thecured composition of claim
 1. 20. A curable epoxy resin composition forencapsulation of a solid state device, which comprises (A) a siliconeepoxy resin comprising1,1,3,3-tetramethyl-1,3-bis[2(7-oxabicyclo[4.1.0]hept-3-yl)ethyl]disiloxane,(B) a hydroxyl-containing silicone resin comprising the hydrolysisproduct of a mixture of phenyltrichlorosilane, methyltrichlorosilane,and dimethyldichlorosilane, (C) a curing catalyst comprisinghexahydro-4-methylphthalic anhydride, and (D) zinc octoate, whereincomponent (A) is present at a level of greater than about 40% by weight;component (B) is present at a level in a range of between about 1% byweight and about 20% by weight; component (C) is present at a level ofless than about 25% by weight; and component (D) is present at a levelin a range between about 0.008% by weight and about 10% by weight basedon the combined weight of silicone epoxy resin (A), hydroxyl-containingcompound (B), curing agent (C), and ancillary curing catalyst (D). 21.The composition of claim 20, further comprising at least one of athermal stabilizer or a UV stabilizer.
 22. The partially curedcomposition of claim
 20. 23. The cured composition of claim 20.